I picked up a can of Rustoleum Painter’s Choice Satin Granite spray paint at the local Home Depot, and it is a surprisingly good match for the dark gray parts of a late Vanagon interior. I test painted an old ammo box and took some pictures. As a color nerd, I can say that the match isn’t exact, but is definitely close enough. I suspect most people wouldn’t notice a difference.
Probably going to pick up a case of this stuff to use on various parts of the van.